docs: def _get_access_from_refresh(self) -> Tuple[str, float]:
          """Uses the stored refresh token to get a new access token.
  
          This method assumes that the refresh token exists.
  
          Args:
              None
  
          Returns:
              new access token and expiration time (from now)
          """
          headers = self._get_authorization_headers()
          data = {
              'grant_type': 'refresh_token',
              'refresh_token': self.refresh_token
          }
          r = self.session.post(self.TOKEN_URL, headers=headers, data=data)
          response_data = r.json()
          return (response_data['access_token'], response_data['expires_in'])